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1. Technical Field
The method and apparatus of the present invention is in the field of lumbar supports having arched apexes that can be varied in height.
2. Prior Art
Lumbar supports that have archable pressure surfaces actuated by traction cables are known. Typically a flexible pressure surface is mounted on guide rails with a bowden cable sleeve attached to one end of the pressure surface and the bowden cable wire attached to the other end. Traction drawing the wire into the sleeve draws the two ends of the flexible surface together arching it towards a seat occupant. These simple devices are unable to raise or lower the apex of the arch created in a significant or controllable manner.
Lumbar supports with arching pressure surfaces that can move the apes of the arch vertically are expensive, complex and bulky. Typically the vertical movement (and usually the arching movement as well) are actuated by electric motors, as in U.S. Pat. No. 5,050,930 to Schuster, et al. and U.S. Pat. No. 5,609,394 to Ligon, Sr. et al. The ability of these units to customize the vertical alignment of an apex arch to an individual users preference are desirable in the market place. However, the size of these units limits the ability to install other devices, such as duct work, in a seat, their complexity decreases their durability and their expense limits their marketability to luxury vehicles.
There is a need in the art for a simple, durable, compact and inexpensive lumbar support capable of varying the apex of it""s arch vertically.
The present invention is a lumbar support that has an archable pressure surface with a vertically variable apex. A flexible, archable pressure surface has a top end and a bottom end, each of which are slidingly mounted on a pair of guide rails. The guide rails have end stops which prevent the archable pressure surface to slide beyond the stops. When the archable pressure surface is flat, the distance between the sliding ends of the archable pressure surface is substantially equal to the distance between the guide rail end stops.
However, when the pressure surface is arched, the distance between the sliding ends of the pressure surface is shorter than the distance between the guide rail end stops. The present invention takes advantage of this gap between an arched pressure surface and the guide rail stops in order to move the arched pressure surface, and it""s apex, up and down.
The guide rails have a mounting bracket which does not move that is substantially half way between the guide rail end stops. The present invention is capable of arching it""s pressure surface with not one, but either of two bowden cables used to apply the traction that draws the pressure surface top and bottom ends towards one another.
A top bowden cable has it""s sleeve anchored at the pressure surface top end and it""s axial sliding wire anchored at the center bracket. A second, bottom bowden cable has it""s sleeve anchored to the bottom of the archable pressure surface and it""s sliding axial wire anchored to the central mounting bracket. Traction drawing the bowden cable wire into the bowden cable sleeve on either of these bowden cables will shorten the distance between the top and bottom ends of the pressure surface, bowing it outwards and creating an arch.
If traction is applied to the top bowden cable, the bowden cable sleeve end draws the top of the archable pressure surface downwards towards the central bracket. This also draws the opposing bottom of the archable pressure surface downwards, where it is stopped by the bottom guide rail stop. Continuing traction draws the pressure surface top end closer to the stopped pressure surface bottom end, causing it to flex outwards. Conversely, traction on the bottom bowden cable draws the bottom of the archable pressure surface towards where the bottom bowden cable wire is mounted on the central bracket. The top of the archable pressure surface is stopped by the top guide rail stop and continuing pressure on the bottom bowden cable pinches the archable pressure surface between the bottom bowden cable sleeve and the top guide rail stop, again flexing the archable pressure surface.
The dimensions of the arch created by these motions is the same if either the top or bottom bowden cable are used to create it. If the top bowden cable is used to create the arch, the arch will be butting the bottom guide rail stop, and if the bottom bowden cable is used the arch will abutting the top guide rail stop. Accordingly, selecting the bowden cable used selects whether the arch is created in a upper-most position or a lower-most position. These positions are separated by several inches.
Tractive forces applied to both bowden cables through a single actuator. The ends of each bowden cable that are not attached to the archable pressure surface are attached to a wheel in the rotating actuator. Rotation of the wheel in one direction applies traction to one bowden cable, and rotation of the wheel in the opposite direction applies traction to the other bowden cable. Thus, at one extreme rotation of the actuator wheel, the pressure surface is fully flexed, fully drawn to the top end of the guide rail and maintains an apex in the top position. Full rotation of the actuator wheel in the opposite rotational direction forms the pressure surface arch on the opposite end of the guide rail. Travel from one actuator wheel extreme through a half-way point and to the other actuator wheel extreme reduces tractive force on one cable, moves through a half-way point where there is no tractive force on either cable and then applies an opposite tractive force on the opposite bowden cable. When the actuator wheel travels through the half-way point where there is no traction on either cable, the archable pressure surface is flat.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.